Telephone system



May 7, 1940. P. BAKKER TELEPHONE SYSTEM Filed Nov. l2, 1938 E 1" Man/ZLATTORNEY5 MR? 7 1940- P. BAKKER 2,199,534

TELEPHONE SYSTEM Find. nov. 12, 193e ssnaetssneet May 7 `1940.

P- BAKKER @Emmons sx-.STEM

3 Sheets-Sheet 3 INVENTOR,

, Fier B akker BYMWMM MM5,

ATTORNEYS.

fiatented^ May 7, Q

UNITED STATES 1PA-rem* orner.

TELEPHONE. sYs'rEM poration off Delaware Application November 12, E938,Serial No.` 239,990

26 Claims.

The present invention relates to automatic; te1e phone-systemsandmoreparticularly to improved line circuits associatedvwith the linesthereof.

In an automatic telephone System, usualli7 a line circuit isindividually associated with each line thereof, which line circuitconventionally comprises separate and distinct line, cut-off and.lockout relays mounted upon a supporting panel. These three relays areordinarily so connected and arranged that the automatic switches in thesystem having. access to a line are controlled in accordance with` thevarious operations thereof to set up, by way of the line, outgoing callconnections from and incoming call connections to a subscribersubst-ation associated with the line, and that the line is; marked asbusy to the automatic switches having access theretov in the event afault appearsk upon the line. Furthermore, these relays are so connectedand arranged that the automatic switches in the system having access tothe line are Controlled in accordance with other operations thereof toset up, by way of the line, reverting call connections between two ofthe subscriber substations associated with the line, in the event. theline is of the multiparty type.

While line circuits of the type briefly described above are entirelysatisfactory in operation, they are more expensive to manufacture and tomaintain in service than is desirable, primarily due to the fact that.three separate and distinct relays are required in each line circuit inorder to render the previously mentioned services by way of theassociated line. Y

In` order to reduce the manufacturing and maintenance costs of linecircuits, improved line circuits disclosed in the copending applicationof Clarence E. Lomax, Serial No. 234,751, filed October 13, 1938, weredeveloped. Also, in the abovefmentioned Lomax application, a combinedline and cut-off relay is disclosed, which is in.- corporated in theimproved line circuits disclosed therein. Briefly, the combinedv lineand cut-off relay disclosed in the above-mentioned Lomax applicationcomprises a support, line and cut-off magnets carried by the support,contact actuating members respectively associated with the magnets, acontact set operatively associated with each of the members, and. alatching arrangement for controlling the operation` of the memberassociated with the line magnet in two steps. The latching arrangementis controlled by the operation of the member associated with the cut-offmagnet and is so constructed and ar ranged that the member associatedwiththe line magnet is only partially operated when the line magnetwinding is energized prior to the energization of the cut-ofi magnetwinding, that this member is fully operated whenthe line. magnet windingisenergized subsequent tor the energiza.-

(or. 17e-17) tion of, the.` cut-ofi magnet; Windng:,. and. that. this y.member is operated from. a partially operated position. to; a. iullyoperated position when the cutroi magnet: winding is energizedsubsequent to. and Whilethe line` magnet` winding is enersized.. The;Contact sets operatively associated these; members; are. controlled inaccordance with the; various operations thereof. Alsof the linecircuits' disclosed in the Dreviously mentioned Lomax application embodylineI and cut-ott magnet. control circuits,l automatic. switch. Controlcircuits and line markirler circuits, whichV are controlled; by theContact sets, and which; .are so connected and arranged that the i`automatic switches in` the system are controlled thereby to render, byway of a subscriber line. with, which the` linecircuit is, associated,calling,v called and reverting callv services to the subscribersubstations associated with the sub scriber line.

Although. the improvements as disclosed in the previously mentioned;Lomax application considerably reduce the manufacturing and maintenancecosts of line circuits, further reductions in these costs are desirable`and. may be realized byv further simplifying ,the` various circuitsembodied in. the line circuits and by employing in the line circuitsimproved combined line and cutoi relays of the construction andarrangement disclosed in the copendingA application of John E. Ostline,Serial No.,240,00l, led November l2, 1938. y The combined. line andcut-ofi vrelay disclosed in the above-mentioned" Ostl'ine. applicationcornprises a sup-port, line and" cut-oli. magnets carried by the.support,` a movable contact actuating member operatively associated withthe line magnet', a, movable contact actuating member operativelyassociated. with the cut-oir. magnet, arst contactl set operativelyassociatedV with the first-mentioned member, a second contact setoperatively associated with the second-mentioned member, a third contactset, and mechanical means for operatively associating the thirdcontactsetwiththe first-mentioned member. Each of the Contact sets hasa, normal position and is 'movable away from its normal position inyresponse to the operation ofthe oneof the members `with which it isoperatively associated. Also, the combinedv line and, cut-oliiv relaycomprises means vfor biasing4 each ot the contact sets to its normalposition, and means, controlled by the. operation of thesecond-mentioned member for releasing the mechanical` means, whereby thethird contact set isno-t moved away from its normalV position in. theevent the first-mentioned member isl operated subsequent to theoperation of the secondrmentioned member andthe third,v contact set isreturned' to. its normal positionv in the eventthe second-mentionedmember is operated subsequent to the operation of the first-mentionedmember. Also, the mechanical means is reset when both of the members arerestored.

Accordingly, it is an object of the present invention to provide animproved line circuit adapted for use in an automatic telephone systemwhich comprises line and cut-oi relays, which two relays are connectedand arranged in an extremely simple manner and so related that theautomatic switches in the system are controlled thereby to render, byway of a subscriber line with which the line circuit is associated,calling, called and reverting call services to the subscribersubstations associated with the subscriber line.

It is another object of the invention to provide an improved linecircuit of the type described adapted for use in an automatic telephonesystem. which is extremely economical to manufacture and which ispositive in operation in order to control the automatic switches in` thesystem in a thoroughly reliable manner, whereby the desired services maybe rendered to the subscriber substations associated with the subscriberlines in the system.

A further object of the invention is to provide an improved automatictelephone system in which there are incorporated improved line circuitsof the type described, each including an improved combined line andcut-off relay of the construction noted.

The features of the present invention are illustrated as beingincorporated in an automatic telephone system including a plurality ofsubscriber lines, some oi the lines being of the multiparty type, eachline having an improved line circuit of the type described incorporatingan improved combined line and cut-01T relay of the construction notedindividually associated therewith, and a number of nder-connector linksfor setting up connections between the various lines. A number ofsubscriber substations are associated with each oi the lines oi themultiparty type; and a distributor of the preselective type is providedfor the purpose oi assigning idle ones of the links to the use ofcalling ones of the lines in a predetermined order.

In accordance with one feature of the invention, the line circuit isadapted for use in an automatic telephone system including a lineaccessible to an automatic switch and comprises, in combination, lineand cut-off relays, a rst contact-set operatively associated with theline relay, a second contact set operatively associated with the cut-offrelay, a third co-ntact set, and means normally eiective operatively toassociate the third contact set with the line relay, each of the contactsets having a normal position and being operative away from its normalposition in response to the operation of the one of the relays withwhich it is operatively associated. Also, the system comprises meansresponsive to the creation of a calling condition on the line forcausing the line relay to be operated, means responsive to the seizureof the line by the automatic switch for causing the cut-off relay to beoperated, means controlled by the operation of the cut-o relay forrendering the rst-mentioned means ineiective, means controlled by theoperation of the second contact set away from its normal position forcausing the line relay to be operated, and automatic switch controlcircuits and line marking circuits governed by the contact sets. Moreparticularly, the means which is normally effective operatively toassociate the kline marked as a calling line.

third contact set with the line relay comprises a blocking or latchingelement which is tripped when the cut-E relay is operated. Furthermore,means is provided for biasing each of the contact sets to its normalposition, whereby the third contact set is not operated away from itsnormal position in the event the line relay is operated subsequent tothe operation of the cutoi relay and the third contact set is returnedto its norma-1 position in the event the cut-oi relay isoperatedsubsequent to the operation of the line relay. Finally, the latchingelement is reset when both of the line and cut-off relays are restored.

In accordance with another feature of the invention, a telephone systemis provided which comprises a line, a number of nder and connectorswitches having access to the line, a line circuit of the connection andarrangement described associated with the line, and a distributorassociated with the nder switches and operative to cause an idle one ofthe nder switches to operate and seize a line marked as a calling line.Also, the system comprises means responsive to the creation of a callingcondition on the line for causing the line relay to be operated, meanscontrolled by the operation of the iirst and third contact sets awayfrom their normal positions for initiating operation of the distributorand for marking the line as a calling line, means responsive to theseizure of the line by one of the iinder switches for causing the cutoirelay to be operated, and means controlled by the operation of thecut-oft relay for releasing the latching element, whereby the thirdcontact set is returned to its normal position. Furthermore, the systemcomprises means controlled by the operation of the second contact setaway from its normal position. for causing the line relay to be retainedoperated, means controlled by the return of the third contact set to itsnormal position for arresting the operation of the distributor, meansfor releasing the one finder switch, means responsive to the release ofthe one finder switch for causing the cut-oli relay to be restored,means controlled by the return of the second contact set to its normalposition for causing the line relay to remain operated in the event acalling condition remains on the line, and means controlled when thefirst contact set is operated away from its normal position and thesecond contact set is returned to its normal position for marking theline as busy to the connector switches.

In accordance with a further feature of the invention, the telephonesystem comprises means controlled by the operation of the iirst contactset away from its normal position for marking the line as busy to theconnector switches and signal means controlled when the iirst contactset is operated away from its normal position and the second and thirdcontact sets are returned to their normal positions.

In accordance with a further feature of the invention, the telephonesystem comprises a line, a plurality of subscriber substationsassociated with the line, a number of iinder-connector links havingaccess to the line, a line circuit of the connection and arrangementdescribed associated with the line, and a distributor associated withthe links and operative to cause the finder switch of an idle one oi thelinks to operate and seize a Also, the system comprises means responsiveto the creation of a calling condition on the line for causing the linedream4 relay to be operated, means controlled by the operation of thefirst and second contact sets away from their normal positions forinitiating operation of the distributor and for marking the line acalling line, means responsive to the seizure of the line by the iinderswitch of the one link for causing the cut-o relay to be operated, andmeans controlled by the operation of the cut-off relay for releasing thelatching element, whereby the third contact set is returned to itsnormal position. Furthermore, the system comprises means controlled bythe operation of the second contact set away fromits normal position forcausing the line relay to be retained operated, means controlled by thereturn of the third con.- tact set to its normal position for arrestingthe operation of the distributor, impulse responsive means included inthe selector switch of the one link and operative to cause ringingcurrent to` be projected by way of the one link over the line subsequentto the termination of the calling condition thereon and to cause theline relay to remain operated, and means responsive to the answering ofthe call at a called one of the substations for causing the one link tobe released and for creating a new calling condition on the line'.Finally, the system comprises means responsive to the release of the onelink for causingr the cutoif relay to be restored, means responsive tothe creation of the new calling condition on the line for causing theline relay to remain operated subsequent toI the return of the secondcontact set to its normal position, and means controlled when the rstcontact set is operated away from its normal position and the secondcontact set is returned to its normal'position for marking the line asbusy to the connector switches of the links.

Further features of the invention pertain to the particular arrangementof the circuit elements thereof, whereby the above-outlined andadditional features are attained.

The novel features believed to be characteristic of the invention areset forth with particularity in the appended claims. The invention, bothas to its organization and method of operation, together with furtherobjects and advantages thereof, will best be understood by reference tothe follo-vving specication taken in connection with the accompanyingdrawings in which Figs. 1 and 2, taken together, illustratediagrammatically a telephone system including improved line circuits andembodying the present invention; Fig. 3 is a perspective view of acombined line and cut-oif relay adapted to be incorporated in the linecircuits shown in Fig. l; and Fig. 4 illustrates diagrammatically thearrangement of the switch springs associated with the combined line andcut-off relay when it is incorporated in theline circuits shownin Fig.l.

Referring now more particularly to Figs. 1 and 2 of the drawings, thetelephone system there illustrated comprises an exchange having apiurality of subscriber lines including the subscriber lines and IBBterminating thereat, and provided with a plurality of finder-connectorlinks including the link ISEF for setting up connections between thevarious subscriber lines. Also a distributor H33 is provided forassigning idle ones of the links to the use of calling ones of thesubscriber v lines; and a number of reverting call switches, includingthe reverting call switch 201i, are provided for the purpose ofprojecting code ringing current over a subscriber line when a revertingcall is initiated thereon. More specifically, the exchange has anultimate capacity of one hundred lines, and the number of linksisdetermined by the amount of traiilc which the exchange is required tohandle, usually ten links being adequate to render satisfactory service.

Each of the links may be identical to the link IEB which comprises afinder-portion or switch lili and a connector portion or switch W2, eachhaving access to each subscriber line in the system. The finder switchand the connector switch included in each link may be one of any of anumber of well-known types. However, it is preferable that each of theseswitches includes a switching mechanism of the Strowger type and theusual control apparatus therefor, the wipers of the switching mechanismincluded in the finder switch lill being illustrated at ISEL'lBi and|82, and the wipers of the switching mechanism included in the connectorswitch 182 being illustrated at i253, 186i and |85. Also the connectorswitch m2 comprises impulse responsive apparatus of any desired type forprojecting code ringing current over an idle called subscriber lineafter it has been seized by the switching mechanism included therein,which is so conf.

nected and arranged that a divided ringing circuit may be employed inthe system. The `distributor H33 may be one of any of a number ofwell-known types. However, it is preferable that the distributor |03 isof the preselective type, such that an idle link is selected to beassigned to the use of a calling line prior to the initiation of a callon the line.

At least a number ci the subscriber lines terminating at the exchangeare of the party type, the subscriber lines l and it) being party lines,each serving a number of subscriber substations, respectively, includingthe subscriber substations A, B and C, D. Each of the subscribersubstations is provided with atelephone instrument, a dial mechanism,and a ringer. The subscriber substations associated with each partylineare arranged in two groups, the ringer at each substation in thefirst group beingl connected between one line conductor of thesubscriber line and ground, and the ringer at each substation in thesecond group being connected between the other line conductor of thesubscriber line and ground, whereby a divided ringing circuit is.employed in the system.

A line circuit is individually associated with each subscriber line inthe system, the line circuit mit being individually associated withv thesubscriber line ld, and the line circuit lii being individuallyassociated with the subscriber line itil. The line circuit IM comprisesa combined line and cut-oir relay including a line magnet or relay RIZGand a cut-off magnet or relay Rl i0; and the line circuit MI5 comprisesa combined line and cut-off relay including a line magnet or relay Ridi!and a cut-01T magnet or relay RiSil. Preferably, the line circuits areof identical connection and arrangement, each comprising `a combinedline and cut-ofi relay of the construction and arrangement of thatdisclosed in the previously mentioned copending lOs'tline applicationand shown in FigS. Also, each of the combined line and cut-off relaysincludes a switch spring assembly of the construction and arrangementshown in Fig. 4.

Each of the reverting call switches' may be identical to the revertingcall switch 20B which comprises two minor switches 23d and 29B, a linerelay R2 30, a hold relay RZ-tk), two transfer relays R260 and R270, aring cut-oit relay R255, aswitchyms Y 'ing-through relay' R228, twocontrol relays RZIU vand R258, the control and controlled circuitstherefor, and a transformer 28|. The minor switch 280 comprises tworotary switches 28| and 282 provided with Contact banks 234 and 286,respectively, and associated wipers 283 and 285, respectively, a rotarymagnet M233 for simultaneously rotating the wipers of the rotaryAswitches 28| and 282, and a release magnet M231 for releasing thewipers of the rotary switches 28| and 282 and for causing these Wipersto be returned to their normal positions. Also two switch springs 238are associated with the wipers of the rotary switches 28| and 282, whichare actuated into engagement when these wipers are rotated by the rotarymagnet M236 away 'from ,their normal positions. The minor switch 299Acomprises two rotary switches 29| and 292 provided with contact banks294 and 299, respectively, and associated wipers 293 and 295,respectively, a rotary magnet M238 for simultaneously rotating thewipers of the rotary switches 29| and 292, and a release magnet M239 forreleasing the wipers of the rotary switches 29| and 292 and for causingthese wipers to be returned to their normal positions. Also two switchsprings 235 are associated with the wipers of the rotary switches 29|and 292, which are actuated into engagement when these wipers arerotated by the rotary magnet M238 away from their normal positions. Alsoit is noted that the reverting call switch 288 is connected and arrangedto project code ringing current over a calling subscriber line by way ofthe trunk line |18 when a connection is established therebetween by wayof an operated one oi the links, in such a manner that a divided ringingcircuit may be employed in the system.

As best shown in Fig. 3 of the drawings, the

A combined line and cut-01T relay which is incorporated in each of theline circuits employed in the system comprises a supporting plateincluding two portions 38| and 382 suitably secured together by anarrangement including a strap 383 and an outwardly extending plate 394.The portions 38| and 382 of the supporting plate respectively carry lineand cut-01T magnets 385 and 389arranged in spaced parallel relationshipwith respect to each other and to the corresponding portions of thesupporting plate, each being provided with a suitable energizingwinding. Also, the magnets 385 and 386 are arranged closelyadj acent toeach other and comprise, together with the portions 38| and 382 of thesupporting plate, a unitary structure. A supporting bracket 381 providedwith two upwardly extending arms 388 carrying a pivot pin 389 is securedto the upper portion 38| of the supporting plate by an arrangementcomprising a screw 318 and a washer 3| I; and a supporting bracket 3|2provided with two upwardly extending arms 3|3 carrying a pivot pin 3M issecured to the upper portion 382 of the supporting plate by anarrangement comprising a screw 3I5 and a washer 3|9. An armature 3|'lprovided with two rearwardly extending arms 3|8 is pivotally supportedon the pivot pin 389 adjacent the pole face of the core of the linemagnet 385; and an armature 3|9 provided with two rearwardly extendingarms 328 is pivotally supported on the pivot pin 3M adjacent the poleface of the core of the cut-off magnet 388. The armature 3H is providedwith a downwardly extending arm 32| having a rearwardly projectingfinger 322 on the outer end thereof extending to the rear of the portion38| ofthe supporting plate adjacent the right-hand edge thereof; and thearmature 3|9 is provided .with a downwardly extending arm 323 having arearwardly projecting finger 324 on the outer end thereof extending tothe rear of the portion 382 of the supporting plate adjacent theright-hand edge thereof. Two contact sets or switch spring assemblies325 and 325, each comprising a plurality of individual flexible switchsprings suitably insulated from each other and from the portion 38| ofthe supporting plate, are secured to the rear side of the portion 38| ofthe supporting plate and cooperate with an insulating button 321 carriedby the nger 322 in such a manner that the individual switch springs inthese switch spring assemblies are actuated into engagement anddisengagement with each other in a predetermined manner, when thearmature 3H is rotated about the pivot pin 389. Also, a contact set orswitch spring assembly 328, comprising a plurality of individualflexible switch springs suitably insulated from each other and from theportion 382 of the supporting plate, is secured to the rear side of theportion 382 of the supporting plate and cooperates with an insulatingbutton 329 carried by the finger 324 in such a manner that theindividual switch springs in this switch spring assembly are actuatedinto engagement and disengagement with each other in a predeterminedmanner, when the armature 3|3 is rotated about the pivot pin 3M.

More particularly, the switch spring assembly 325 comprises a spring 339provided with a flexible rearwardly extending flange or latching element33| which normally abuts or engages the upper portion of a spring 332included in the switch spring assembly 326. Accordingly, when thearmature 3|? is rotated in a clockwise direction about the pivot pin389, as viewed in Fig. 3, the insulating button 32T carried by theiinger 322 engages the spring 338 and flexes the upper portion thereofrearwardly. This rearward movement of the spring 338 actuates theindividual switch springs included in the switch spring assembly 325into engagement and disengagement with each other in a predeterminedmanner more fully described subsequently. Furthermore, the flange 33|provided on the upper portion of the spring 338 engages the upperportion of the spring 332 and flexes the upper portion thereofrearwardly. This rearward movement of the spring 332 actuates theindividual switch springs included in the switch spring assembly 328into engagement and disengagement with each other in a predeterminedmanner more fully .described subsequently. When the armature 3| 9 isrotated in a clockwise direction about the pivot pin 3M, as viewed inFig. 3, the insulating button 329 carried by' the linger 324 engages aswitch spring 333 ineluded in the switch spring assembly 328 and fleXesthe upper portion thereof rearwardly. This rearward movement of theswitch spring 333 acytuates the individual switch springs included inthe switch spring assembly 328 into engagement and disengagement witheach other in a predetermined manner more fully described subsequently.

As previously noted, the switch spring assemblies 325 and 328 arenormally simultaneously actuated away from their normal positions by themovement of the armature 3H. However, an arrangement is provided forrendering the actuation of the switch spring assembly 325 independent ofthe actuation of the switch spring assemadjacent the upper portionthereof bly 326 and for releasing the switch spring asprising a bearingportion rotatably secured between the rear wall of the portion 302 ofthe supporting plate and a tab 335 formed integral with the strap 303and arranged closely adjacent to the rear wall of the portion 3D2 of thesupporting plate. Furthermore, the rocking bar 333 comprises anoutwardly and downwardly extending arm 336 arranged in the path ofmovement of the arm 323 carried by the armature 3I9 and an outwardly andrearwardly extending arm 33? arranged beneath the flange 33I provided onthe upper portion of the spring 333 included in the switch springassembly 325. When the'armature 3I9 is rotated in a clockwise directionabout the pivot pin 3M, the arm 323 thereon engages the arm 336 on therocking bar 236, thereby to cause the rocking bar to be rotated in aclockwise direction upon its bearing, as viewed in Fig. 3. When therocking bar 334 is rotated in a clockwise direction upon its bearing,the arm 33T thereof engages the ange 33I provided on the upper portionof the spring 330 included in the switch spring assembly 325 and flexesthe flange 33I upwardly and out of abutting relation with the upperportion of the spring 332 included in the switch spring assembly 32E. Atthis time, if the armature 3II occupies a non-operated position and issubsequently operated, only the switch spring assembly 325 will beactuated. However, if the armature 3H occupies an operated position, theswitch spring assembly 32B will be released and returned to its normalposition due to the fact that the outer end of the flange 33I providedon the upper portion of the spring 33D is flexed out of abuttingrelation with the upper portion of the spring 332. Thus, it will beapparent that in the event the winding .of the line magnet 335 isenergized prior lto the energization of the winding of the cut-0E magnet335, the switch spring assemblies 325 and 326 are simultaneouslyactuated away from their normal positions. However, in the event thewinding of the cut-ofi magnet 335 is energized prior to the winding ofthe line magnet 335, only the switch spring assembly 325 is actuatedupon the energization of the winding of the line magnet 335. Finally, inthe event that-the winding of the cut-oir magnet 305 is energizedsubsequent to the energization of the winding of the line .magnet 335,the switch spring assembly 323 is released and returned to its normalposition when the winding of the cut-oir magnet is energized. The switchspring assembly 328 is actuated away from its normal position directlyin .accordance with the energization of the winding of the cut? offmagnet 33t and the actuation thereof is independent of the sequence ofenergizing the windings of the line and cut-off magnets 335 and 333,respectively.

Referring now more particularly to Fig. fi of the drawings, it will beobserved that the switch spring assemblies associated with the line `andcut-oir magnets R123 and RI I 0, respectively, corresponding to theswitch spring assemblies incorporated in the line circuit IM, are soconstructed and arranged that, when the line magnet RIQD is energized,the armature indicated at 3ia is rotated in a clockwise direction aboutthe pivot pin 339e, thereby to cause the insulating button 327e carriedthereby to ex the upper portion of the .spring 33Go. This movement ofthe spring 330e ,is eiiective to actuate the switch spring assembly325e, thereby to move the switch springs RAI25 and RCI25 intoengagement, yto move the switch springs RAIZI and RCI22 intodisengagement, and to move the switch springs RAIZI and RCI23 intoengagement. Also, this movement of the spring 333e causes the flange33Ia carried by the upper portion thereof to engage the spring 332aincluded in the switch spring assembly 326e, thereby to actuate thelatter switch spring assembly. This actuation of the switch springassembly 326e is effective to move the switch springs RAI26 and RCI23intodisengagement, to move the swtich springs `RAI23 and RCI2I intoengagement, and to "move the switch springs RAiM and RCIZIi intoengagement. This movement of the switch springs RAIZi, RCIM and RAI26,RCI'Z'I is effective tov close the R contacts associated therewith; andthis movement of the switch springs RAIZB, RCIZSv is eiective to openthe Rv contacts asso ciated therewith. Subsequently, when the cut.`

ofi magnet RI III is energized, the armature indicated at 3| 9a isrotated in a counterclockwise direction about the pivot pin' llia,thereby to cause the insulating button 3290, carried thereby to vengagethe switch spring 333e included in the switch spring assembly 328e andiiex the upper portion thereof, thereby to actuate the individual switchsprings included in this switch spring assembly. 'This movement of theswitch spring 333e is eiiective to move the switch springs RAI Il! andRCIM into engagement, thereby to close the X contacts associatedtherewith. Subsequent movement of the switch spring 333e is effective tomove the switch springs RAI I3 and' RCII3 into disengagement, to movethe switch move the switch springs RAI I2 and RCI I2 into engagement, tomove theswitch springs RAIlii and RAI i-'I into engagement, and finally,to move the switch springs RAI Il and RCI Il into dischgagement. Finalmovement of the switch spring 3330I is eiiective tov move the switchsprings RAI I-I and RCIII into disengagement, thereby to open the lYcontacts associated therewith.

Also, when the armature 3l9a is rotated in a counterclockwise directionabout the pivot 'pin 3I4a, the arm 336e of the rocking bar 333e isengaged, thereby to cause the rocking bar to be rotated in a clockwisedirection about its pivot. This `rotation of .the rocking 4bar 333e isveffective to cause the arm 33M thereof to flex the outer end of .theange 33m provided on the upper portion of the spring 333e included inthe switch spring `assembly 3250. out of engagement with the upperportion of the spring 33211. included in the switch spring assembly326e; The switch spring assembly 326e is then released and theindividual switch springs thereof are actuated to their normalpositions, therebyto move the switch springs RAIN, RCIM and RAIZB,RCI2'I into disengagement and to move the switch springs RAIZE, RCI28into engagement. Also, it is .noted that in the event the cut-off magnetRI Ill is energized prior to the energization of the line .magnet RI 23,

switch spring assemby 326er. Accordingly, when the line magnet RIZ@ isthen energizedonly the switch spring assembly 325a is actuated. in thepreviously described manner.

The connection and arrangement of the system will best be understoodfrom a consideration of the following description, with reference tolFigs. 1 and 2 of the drawings, of the operation of the apparatusincorporated therein to set up the different connections between thevariousv subscriber lines.

. completed between the line conductors of the subscriber line |50, abridge circuit is completed for energizing in series the upper and lowerwindings of the line magnet RI20 in the line circuits I04 individuallyassociated with the subscriber line |50, which extends from battery atthe upper winding of RI20 by way of the upper winding of RI20, RAI I I,RCI I I, CI5I, the bridge path at the substation A between CI5I andCI52, CI52, RCIIl, RAIIl and the lower winding of RI20 to ground. Whenenergized over the abovetraced circuit, the line magnet RI20 operates,thereby to actuate the two switch spring assemblies associated therewithin order to close the R contacts associated with the switch springsRAI24, RC|24 and RAIZB, RCI21, and to open the R contacts associatedwith the switch springs RA|26 4and RCI28. More particularly, the linemagnet RIZ@ completes, at RAI25 and. RCI25 and at RAIEB and RCI21, apath for applying ground potential to the start conductor CISi)extending into the distributor I 03, this path extending from ground atRCI I5 by way of RAI I5, RCI25, RAI25, RAIZS, RCI21 and CISI to thestart conductor C |90. This application of ground potential to the startconductor CISU initiates the operation of the distributor |03 and causesthe distributor to operate and assign the previously selected idle linkto the use of the calling subscriber line |50. Assuming that theillustrated link |00 is assigned by the distributor I 03 to the use ofthe calling subscriber line |50, the distributor also marks with groundpotential by way of the conductor CI 93 the level in the contact bank ofthe Strowger mechanism included in the finder switch 0|, wherein thecalling subscriber line |50 terminates. Also, the line magnet RI20completes, at RAI2|| and RCI24, a path for applying battery potential tothe control conductor C |53, this path extending from battery at theupper winding of the cut-01T magnet RIIIl' by Way of the upper windingof Rl I0, RAIM and RCI21! to thc control conductor CI53. Thisapplication of battery potential to the control vconductor CI53 marksthe radial position of the contact set in the level in the contact bankof the Strowger mechanism included in the nder switch wherein thesubscriber line |50 terminates. Further, the line magnet R|20 completes,at RAI2| and RCIZ3, a path for applying ground potential to the controlconductor CI 54 of the subscriber line |50 extending to the contactbanks of the Strowger mechanisms included in the connector switches ofthe links having access thereto, thereby to mark the subscriber line |50as busy thereto immediately and prior to the time the finder switch |01of the link |00 operates to seize this subscriber line, this pathextending from ground at RCII3 by way of RAII3, RC|23 and RAIZI to thecontrol conductor CI54.

The Strowger mechanism included in the nder switch lill then operates tomove the wipers |80, I8| and |82 thereof in the vertical direction tothe level wherein the calling subscriber line |50 terminates. ThisStrowger mechanism then operates to move the wipers thereof in theradial direction to the radial position of the contact set wherein thecalling subscriber line |50 terminates, at which time the wipers |30 and|82 thereof engage the contacts terminating the line conductor C|5| andCI52, respectively, and the wiper |8| engages the contact terminatingthe control conductor CI53 of the calling subscriber line |50. Thepresence of battery potential upon the control conductor C|53 completesa circuit for energizing a relay in the finder switch |0I operative toarrest further operation of the Strowger mechanism included therein,which relay also operates to complete a path for applying groundpotential to the wiper 58 I. This application of ground potential to thewiper ISI completes a circuit for energizing in multiple the upper andlower windings of the cut-off magnet RIIO. This circuit extends from thegrounded wiper |8I by way of the contact terminating the controlconductor CI53 to CI53, one branch of this path extending from CI53 byway of RCIZA, RAI 24 and the upper winding of RI I0 to battery, and theother branch of this path extending from CI53 by way of RAII4, RCII4 andthe lower winding of RIIO to battery. Also, this application of groundpotential to the wiper I 8| prepares a path, traced hereinafter, forapplying ground potential to the control conductor` CI54 of thesubscriber line |50 extending to the contact banks of the Strowgermechanism included in the links of the connector switches having accessthereto, thereby subsequently to mark the subscriber line |50 as busy tothe connector switches of these links. When energized over theabove-traced circuit, the cut-olf magnet RI I0 operates to complete, atRAI IIS and RAI I'l, a holding circuit for energizing the lower windingof the line magnet RIZIJ, this circuit extending from battery at theresivstor |51 by way of the resistor |51, RAII6. RAI I1 and the lowerwinding of RI20 to ground.

Also, the cut-ofi magnet RII!! interrupts, at

RAII'I and RCI|`| vand at RAIII and RCIII, points in the `originalbridge circuit for energizing the upper and lower windings of the linemagnet RI 20, thereby to free the line conductors CI 5I and C|52 of thesubscriber line |50 of impedance elements. Further, the cut-off magnetcompletes, at RAII?! and RCII2, and at RAIN and RCI I4, the previouslymentioned path for applying ground potential to the control conductorCI54, this path extending from the grounded wiper I8| by way of thecontact terminating the control conductor CI53, CI53, RAII4, RCIM, RAII2 and RCI l2 to the control conductor CI54. Further, the cut-off magnetRI I0 interrupts, at RAII3 and RCIIS, a point in the previously tracedpath for applying ground potential at RC! I3 to the control conductorCI54 and interrupts, at RAI I5 and RC'II5, a point in the previouslytraced path for applying ground potential at RCII5 to the start leadCI90 extending into the distributor |03. Also, upon operating, thecut-off magnet RIIil releases the latching arrangement for retaining therestoring switch spring assembly associated with the line magnet R12!!in its actuated position, 'thereby -to allow the individual switchsprings included in this switch spring assembly to be returned to theirnormal positions. More particularly, the switch springs RAl2ll andRCl2Ll are moved into disengagement,

thereby to open the R contact associated therewith; and the switchsprings RAlZB and RClZ'i are moved into disengagement, thereby to openthe R contact associated therewith. Finally, the switch springs RAIZBand RCIZB are moved into engagement, thereby to close the R contactassociated therewith. Whenl the R contact associated with the switchsprings RANA and RCIM y is opened, the previously traced circuit forenerv er winding thereof.

' gizing the upper winding of the cut-oit magnet RIID is interrupted,this magnet being retained in its operated position at this time due tothe completed holding circuit for energizing the low- When the R contactassociated with the switch springs RAIEB and RC`I2'i is opened, afurther point in the path for applying ground potential to the startlead CI Sil extending into the distributor lll?, is interrupted, andwhen the R contact associated with the v switch springs RAi 2@ and RClZis closed, a point in a. circuit, traced hereinafter, is prepared forapplying ground potential to the control conduct-or CIBG extending to apermanent alarm device. Also, at this time, the line magnet Rl2tlremains in its operated position due to the corn-v pleted holdingcircuit for energizing the lower winding thereof. When ground potentialis removed from the start conductor Cl9 extending into the distributorEES, the distributor H33 operates to'select an idle link in the group oflinks to be assigned to 'the use of the next calling subscriber line,and when the finder switch I lll seizes the calling subscriber lineIlle, the connector switch EQ2 operates to condition the Strowgermechanism included therein to be responsive to dialed digits.

The subscriber at the substation A then dials the first digit of thedirectory number of vthe called subscriber line at the dial mechanismthereat, thereby to transmit a rst series of 'impulses over the loopcircuit extending by way of the subscriber line 15% between thesubstation A and the connector switch m2. Impulse responive apparatus inthe connector switch MIZ operates in response to this iii-st series ofimpulses in order to cause the wipers ISS, iSd, and IS5 olthe Strowgermechanism included therein to be moved in the vert-ical direction to thelevel in the contact bank therein, wherein the called subscriber lineISB is terminated. The subscriber at the substation A then dials thesecond digit of the directory number of the called subscriber line atthe dial mechanism thereat, thereby to transmit a second series ofimpulses by way of the previously mentioned loop circuit to theconnector switch lili? in order to cause the wipers noted of theStrowger mechanism included therein to be moved in the radial directionto the position of the contact set in the contact bank. therein, whereinthe called subscriber line I6!) is terminated. The subscriber at thesubstation A then dials the vthird digit of the Vdirectory number of thecalled substation C at the dial mechanism thereat, thereby to transmit athird series or impulses b-y Way of the previously mentioned loopcircuit to the connector switch le? in order toA At lthis time thelwipers |83 and .E85 engage the contacts in the contact bank terminatingthe line conductors Cii and CM2, respectively, and the wiper IM engagesthe contact-in the contact bank terminating the control conductor CI G3of the called subscriber line Id. At this time ground potential appearsupon the control conductor CI63 in the event the called subscriber linei60 is busy. On the other hand, battery potential appears upon thecontrol conductor Clll in the event the called subscriber line i60 isidle.

Assuming that the called subscriber line I6 is busy, ground potentialderived in the line circuit m5 appears upon the control conductor CI63thereof, thereby to complete a path for energizing a busy relay includedin the connector switch It?, which busy relay operates to cause busytone current to be returned over the loop circuit eX- tending to thec'alling'subscriber substation A., in the usual manner. The productionof busy tone in the receiver of the telephone instrument at the callingsubstation A indicates to the subscriber thereat that the desiredconnection cannot immediately be had due to the busy condition of thecalled subscriber line IEB. The subscriber at the calling substation Athen releases the operated link Iill and the line circuit 9M byreplacing the receiver of the telephone instrument at the substation Aupon its hook. The exact manner in which these operated pieces ofapparatus are released is described in detail hereinafter.

Assuming that the called subscriber line It@ is idle, battery potentialappears upon the con trol conductor Cieli thereof, this batterypotential being derived at 'the lower winding of the cutol magnet RIMiand extending 'therefrom by way' of the lower winding of RIBU, RCifl'Zand RAIG'I to the control conductor C163. This application 'of batterypotential to the control conductor C563 completes a path forshor't-circuiting the busy relay 'included in the connector switch llZ,thereby to cause the connector switch m2 to opera't'e and projectringing current of 'the previously selected code over the calledsubscriber line I 6E in order to cause the ringer at the substation C tooperate in a characteristic manner. This characteristic operation 'cithe ringer at the substation C indicates to the subscriber'thereat thatthe substation C is the called substation. Also, a switch-through relayin the connector switch Iil2 operates to apply direct ground potentialto the wiper ist. This application of direct ground potential to thewiper it completes a circuit for energizing the lower winding or thecut-ofi magnet Rls'l, this circuit extending from the grounded wiper ltdby way of the contact terminating 'the control' conductor CIEM, C'l',RAIdI, RClll and the lower winding of R to battery. When energized overthe above-traced circuit, the cut-oir magnet Rist operates to complete,at RAIEZ and RCE-32, a holding circuit for energizing the lower windingthereof, this circuit oxtending from the grounded control con ductorCIS?) by way of ROSSE, RAISE and the lower winding of Ried to battery.Also, the cutoi magnet Ritt completes, at RAll and RC'IM, a path forapplying ground potential to the control oonductor Cite of thesubscriber line ISU extending to the contact banks of the Strowgermechanisms included in 'the' uder switches of the links having accessthereto, thereby to mark the subscriber .line itil as busy thereto, thispath extending .from the grounded control conductor to the controlconductor C164. Further, the cutol magnet R|30 interrupts, at RA|33 andRCI33, a path in the circuit for applying ground potential to thecontrol conductor C|63 when the line magnet RI40 operates, andinterrupts, at RAI35 A and RCI35, a point in the path for applyingground potential to the start conductor C extending into the distributor|03. Finally, the cut-01T magnet R|30 interrupts, at RAI 3| and RCI3|and at RAIS'I and RCI3I, points in the bridge circuit for energizing theupper and lower windings of the line magnet R|40 and completes, at RA|36and RAI3l, a holding circuit for energizing the lower winding of theline magnet R|40, this holding circuit extending from the battery at theresistor IGT by way of the resistor IB'I, RAISE, RAISI and the lowerwinding of R|40 to ground. Also, upon operating, the cutoi magnet R|30releases the latching arrangement for causing the two switch springassemblies associated with the line magnet R|40 to be actuatedsimultaneously.

When energized over the above-traced circuit, the line magnet R|40operates to actuate only the switch spring assembly directly associatedtherewith, thereby to interrupt, at RAI4| and RC |42, a point in thepreviously traced original circuit for energizing the lower winding ofthe cut-01T magnet R|30. 'I'he subscriber at the substation C thenanswers the call by removing the receiver of the telephone instrumentthereat from its hook, thereby to cause the connector switch |02 tooperate in order to interrupt the projection of ringing current over thecalled subscriber line and to complete an established communicationconnection between the calling subscriber line |50 and the calledsubscriber line |80 by way of the operated link |00.

Assuming that the release of this' established connection is under thecontrol of the last subscriber to replace the receiver of the telephoneinstrument at his substation upon its hook, when the last subscriber atone of the substations replaces the receiver of the telephone instrumentthereat upon its hook, the operated link |00 is released in the usualmanner, thereby to interrupt the established connection extendingbetween the subscriber lines |50 and |50. When the link |00 is released,ground potential therein is removed from the wiper lI, thereby tointerrupt the previously traced holding circuit for energizing the lowerwinding of the cut-ofi magnet RI I0. The cut-off magnet RI I0 thenrestores to interrupt, at RAI I4 and RCI I4, a further point in theholding circuit for energizing the lower winding thereof and a point inthe path for applying ground potential to the control conductor C I 54extending to the contact banks of the Strowger mechanisms included inthe connector switches of the links having access thereto. Also, uponrestoring, the cut-off magnet R! I0 interrupts, at RAII2 and RCI I2, afurther point in the previously traced path for applying groundpotential to the control conductor CI54, prepares, at RAI I3 and RCI I3,a point in the previously traced path for applying ground potential, atRCI I3, to the control conductor CI 54, and prepares, at RA||5 andRCII5, a point in the previously traced path for applying groundpotential, at RCI I5, to the start co-nductor CI 90 extending into thedistributor |03. Finally, the cut-oi magnet RI I0 interrupts, at RAI I6and RAI Il, a point in the previously traced holding circuit forenergizing the lower winding o the line magnet RI and prepares, atRAII'I and RCI and at RAIII and RCIII, points in theI previously tracedbridge circuit for energizing the upper and lower windings of the linemagnet RI20.

The line magnet RI20 then restores to complete, at RAIZI and RCI 22, thepreviously traced path for applying battery potential, at the lowerwinding of the cut-01T magnet RI I0, to the control conductor C154.extending to the contact banks of theV Strowger mechanisms included inthe connector switches of the links having access thereto, thereby tomark the subscriber line |50 as idle. Also, the line magnet RI20interrupts', at RAI 2| and RCI23, a point in the previously traced pathfor applying ground potential, at RCI I3, to the control conductor C|54and interrupts, at RA| and RCI25, a further point in the previouslytraced path for applying ground potential, at RCI I5, to the startconductor CI90. Finally, the line magnet RI20 interrupts, at RA|25 andRCI 25, a point in a path, traced hereinafter, for applying groundpotential to the control conductor C|56 extending to a permanent alarmdevice. Also, it is noted that when both the cut-ofi magnet R||0 and theline magnet RI20 restore, the latohing arrangement for causing the twoswitch spring assemblies associated with the line magnet RI20 to beactuated simultaneously is reset. At this time the subscriber line |50is marked as idle to the nder and connector switches of the links havingaccess thereto and the line circuit |04 is completely released.

Also, when the link |00 is released, ground potential therein is removedfrom the wiper |84, thereby to interrupt the previously traced holdingcircuit for energizing the lower winding of they cut-off magnet R|30.The cut-off magnet R| then restores, thereby to interrupt, at RA|32 andRCI32, a further point in the holding circuit for energizing the lowerwinding thereof and a point in the previously traced path for applyingground potential to the control conductor C104 of the subscriber line|60 extending to the contact banks of the Strowger mechanisms includedin the nder switches of the links having access thereto, thereby to markthe subscriber line |60 as idle. Also, the cut-off magnet R|30interrupts, at RAI34 and RCI34, a further point in the previously tracedpath for applying ground potential to the control conductor CIB4.Further, the cut-off magnet R|30 prepares, at RAI33 and RCI33, a pointin the path for applying ground potential, at RC 33, to the controlconductor C163 of the subscriber line |00 extending to the contact banksof the Strowger mechanisms included in the connector switches of thelinks having access thereto, and prepares, at RAI35 and RCI 35, a pointin the path for applying ground potential, at RCI35, to the startconductor C190 extending to the distributor |03. Finally, the cut-offmagnet R|30 prepares, at RAI3| and RC|3I and at RAI3I and RCISI, pointsin the bridge circuit for energizing the upper and lower windings of theline magnet R| and interrupts, at RAI 36 and RAI3'I, a point in thepreviously traced holding circuit for energizing the lower winding ofthe line magnet RI40.

The line magnet R|40 then restores to complete, at RAI4I and RCI42, apoint in the previously traced path for applying battery potential, atthe lower winding of the cut-off magnet R|30, to the control conductorC|63 of the subscriber line |60 extending to the contact banks of theStrowger mechanisms included in the connector switches of the linkshaving access thereto, thereby to mark the subscriber line |50 as so; i

fas

.Strowger mechanism idle. Also, the line magnet RI40 interrupts, atRA|4| and RCI 43, a point in the path for applying ground potential, atRCISS, to the control conductor C|63. Finally, the line magnet R|40interrupts, at RA|45 and RC|45, a further point in the path for applyingground potential, at RCl35, to the start conductor CI90 and interrupts,at RAME and RC|45, a point in the path for applying ground potential, atRCI35, to the control conductor Cl extending to the permanent alarmdevice. Also, it is noted that when both the cut-off magnet R|30 and theline magnet R|40 restore, the latching arrangement for causing the twoswitch spring assemblies associated with the line magnet RMD to beactuated simultaneously is reset. At this time the subscriber line |60is marked as idle to the nder and connector switches of the links havingaccess thereto and the line circuit |05 is completely released.

It will be understood that a call which is to be extended from thesubscriber substation C to the subscriber sub-station A is firstinitiated at the substation C by removing the receiver of the telephoneinstrument thereat from its hook and is subsequently completed to thesubstation A in the same manner that the previously described call fromthe substation A was extended to the substation C. The release of thisestablished connection is under the control of the last party to replacethe receiver of the telephone instrument at his substation upon itshook, as previously noted. l

A reverting call which is to be extended from the subscriber substationA to ythe subscriber substation B is rst initiated at the substation Aby removing the receiver of the telephone instrument thereat from itshook, thereby to complete the previously traced bridge circuit forenergizing the upper and lower windings of the line magnet R|20. Whenthus energized, the line magnet R|20 operates, as previously explained,in order to complete, at RA|2| and RCI23, the previously traced path foryapplying ground potential to the control conductor C154 of thesubscriber line |50 extending to the contact banks of the Strowgermechanisms included in the connector switches of the links having accessthereto, thereby to mark the subscriber line |50 as busy immediately.Further, the line magnet R|20 completes, at RAIZ!! and RCIZQ, thepreviously traced path for applying battery potential, at the upperwinding of the cut-off magnet RI I0, to the control conductor C|53 ofthe subscriber line- |50 extending to the contact banks of the includedin the lnder switches of the links having access thereto, thereby tomark the radial position of the contact sets in the contact banksterminating the subscriber line |50. Finally, the line magnet R|20completes, at RAI25 and RC|25 and at RAIZG and RCI 27, the previouslytraced path for applying ground potential, at RCI I5, to the startconductor C190 extending into the distributor |03. This application ofground potential to the start conductor C|90 causes the distributor |03to operate to assign a previously selected idle link in the group oflinks to the use of the calling subscriber line |50. Assuming that theillustrated link |il is assigned to the use of the callf ing subscriberline |50, this application of ground potential to the start conductorCIGS and this application of battery potential to the control conductorC|53 marks the position of the contact vset -in the contact bank of theStrowger links having access mechanism included in the finder switch |0|at which the subscriber line |50 is terminated. The nder switch |0| thenoperates, in the previously described manner, thereby to seize thecalling subscriber line |50. When the callingr subscriber line |50 isseized, the cut-off magnet RI I0 operates to release the. latchingarrangement for restraining the restoring switch spring assemblyassociated with the line magnet R|20 in its .actuated position and tocomplete, at RAIM and RCI HI, the previously traced holding circuit forenergizing the lower winding thereof. Also, the cut-oli magnet R||0completes, at RAIIG and RAI the previously traced holding circuit forenergizing the lower winding of the line magnet Rl20, completes, atRA||2 and RCI I2, the previously traced path for applying groundpotential to the control conductor CI54 of the subscriber line |50,thereby to mark the subscriber line |50 as busy to the connectorswitches of the thereto, interrupts, at RAIII and RC||| and at RAIIT andRCII'l, the previously traced bridge circuit for energizing the windingsof the line magnet R|20, and interrupts, at RAI and RCI l5, thepreviously traced path for applying ground potential to the startconductor C|90. The restoring switch spring assembly associated with theline magnet R|20 then restores to its normal position, as previouslynoted, thereby to interrupt, at RA|24 and RCiM, a point in the holdingcircuit for energizing the upper winding of the cut-oli" magnet RI I0,to interrupt, at RA|26 and RCIBT, a further point in the previouslytraced path for applying ground potential to the start conductor C|90,and to prepare, at RAiZS and RCIZB, a point in the previously mentionedcircuit for applying ground potential, at RCII5, to the controlconductor C156 extending to the permanent alarm device. At this time theline and cut-oir` magnets R|20 and RI I0, respectively, are completelyoperated, and the restoring switch spring assembly associated with theline magnet RI 20 is restored to its normal position, as previouslynoted.

The connector switch |02 is conditioned to be responsive to a series ofdialed digits at this time. The subscriber at the substation A thendials at the dial mechanism thereat successively two predetermineddigits into the connector switch |02, thereby to cause the connectorswitch to operate and select the rst trunk line terminating thereat towhich an idle reverting call switch is connected. When these twopredetermined digits are successively dialed the connector switch |02operates as a trunk hunting` connector switch in order to select a trunkline associated with an idle one of the reverting call switches or toreturn busy tone current over the loop circuit extending to the callingsubscriber substation A in the event that all of the reverting callswitches are busy. Assuming that the illustrated reverting call switch200 is the first idle switch, the connector switch |02 operates to seizethe trunk line |10 extending thereto. The reverting call switch 200 ismarked as idle or busy, respectively, by the presence of battery orground potential upon the control conductor CH2 of the trunk line |10.At this time, the reverting call switch 200 being idle, batterypotential appears upon the control conductor CH2 of the trunk line |'|0,the path for connecting battery potential to the control conductor C|'|2extending from battery at the resistor 200 by way of the resistor206,*RA21I, RCZ42, RAMI, and 75 RAN@ to the control conductor C122. Whenthe connector switch i132 selects the trunk line II extending to theidle reverting call switch 23D, further operation thereof is arresteddue to the presence of battery potential upon the control conductor CH2thereof, in the usual manner.

When the trunk line Iii! is thus seized by the connector switch Iii2,this connector switch operates to complete a loop circuit between thecalling subscriber substation A and the line relay R23l in the revertingcall switch 22S, this loop circuit extending from ground at the lowerwinding of R233 by way oi the lower winding of R232, RC229, and RAEil toCH3, and from battery at the upper winding ci R235 by way of the upperwinding of R235, RCQZ, and RA22I to Ci'l, the line conductors Ci'ii andCH3 of the trunk line ill] being connected by way of the operated linkiiil? to the line conductors CISI and CI52, respectively, of the callingsubscriber line E58, and the telephone instrument at the substation Abeing included in a bridge path extending between the line conductorsCiti and (N52 of the subscriber line 58. When energized over theabove-traced circuit the line relay R232 operates to complete, at RA23iand RC222, an obvious circuit for energizing the hold relay R249. Whenthus energized the hold relay R24@ operates to interrupt, at RAEM andRC'liif, a point in the path for applying battery potential to thecontrol conductcr CH2 of the trunk line i'it, and completes, at RAMI andRCEAiS, a path for applying ground potential to the control conductorCH2, this path extending from ground, at ROMS, by way of RAZiI, andRA255 to the control conductor C5212. This application of groundpotential to the control conductor CH2 of the trunk line I'Ill marksthis trunk line as busy to the connector switches oi the links havingaccess thereto, and causes the switch-through relay in the connectorswitch H32 to operate. When the switch-through relay in the connectorswitch M2 operates, ground potential in the operated link ISS is removedfrom the wipers I8! and i 811 of the nder and connector switches IGI andI2, respectively, the link Ill and the line circuit iut being retainedin its operated position at this time due to the application of groundpotential to the control conductor CH2 of the trunk line lill. Also,upon operating, the relay R240 prepares, at RAME, a point in an impulsecircuit traced hereinafter for energizing the rotary magnets M236 andM235 of the minor switches 28S and 292i, respec tively, included in thereverting call switch 255i).

The subscriber at the calling substation A then dials at the dialmechanism thereat a third digit corresponding to the last digit of thedirectory number of the calling substation A, thereby to transmit aseries of impulses by way of the previously mentioned loop circuit tothe line relay R232. The relay R23!) follows the dialed impulses in theusual manner, restoring each time the loop circuit is interrupted andoperating each time the loop circuit is completed. Each time the relayR232 restores, it interrupts, at RAZSi and RC232, the circuit forenergizing the hold relay R246, and completes, at RAZSi and RC233, acircuit for energizing in multiple the relay R259 and the rotary magnetM236 of the minor switch 23S. lThe last-mentioned circuit extends fromground, at RA234, by way of RC233, RAME, and RA262 to R026@ one branchof this circuit extending from RCZGi by way oi the winding of R250 tobattery, andthe other branch extending from RCZBIi by way of RA2I3,RC2T6, and the winding of M2M to battery. The relays R240 and R250,being of the slow-to-release type, remain operated during impulsing.Each time the circuit for energizing the rotary magnet M236 is completedand interrupted, this magnet operates to drive the wipers 283 and 285 ofthe rotary switches 28| and 282, respectively, included in the minorswitch 285 one step away from their normal positions. When the wipersnoted of the rotary switches 223i and 282 are driven away from theirnormal positions, the switch springs 232 are actuated into engagement,thereby to prepare a circuit traced hereinafter for energizing thetransfer relay R 210, this circuit being interrupted at this time, atRA25i, by the operated relay R252. In response to this digit the wipers283 and 285 of the rotary switches 28 and 282, respectively, are drivena number of steps away from their normal positions corresponding to thisdialed digit and into engagement with correspending contacts in theassociated contact banks 284 and 286, respectively. At the conclusion ofthe third digit the line relay R236 reoperates, thereby to interrupt, atRA23I and RC233, the circuit for energizing in multiple the relay R252and the rotary magnet M236 in order to cause the relay R25t to restoreshortly thereafter and to arrest further operation of the rota-ry magnetM236. Upon restoring, the relay R259 completes, at RA25I, the previouslymentioned circuit for energizing the transfer relay R216, this circuitextending from ground, at the switch springs 23d, by way of the switchsprings 234, RAZBI, and the winding of R27@ to battery. When thusenergized the relay R2'iil operates to complete, at RA2'I2, an obviousholding circuit for energizing the winding thereof, to interrupt, atRAUS and RCZ'MS, a further point in the previously traced circuit forenergizing the rotary magnet M236, and to prepare, at RA2i3 andv RCN/i,a point in a circuit traced hereinafter for energizing in multiple therelay R259 and the rotary magnet M238 of the minor switch 29d.

The subscriber at the calling substation A then dials at the dialmechanism thereat a fourth digit corresponding to the last digit of thedirectory number of the called substation B, thereby to transmitanotherl series of impulses by way of the previously mentioned loopcircuit to the line relay R239. dialed impulses in the usual manner.Each time the relay R235] restores it interrupts, at RA23I and RC232,the circuit for energizing the hold relay R226, and completes, at RA23Iand RC233, the previously mentioned circuit for energizing in multiplethe relay R255) and the rotary mag net M238 of the minor switch 29E).The lastmentioned circuit extends from ground, at RA23I, by way ofRC233, RA245, and RA262 to RCZi, one branch of this circuit extendingfrom RC2GII by way of the winding of R250 to battery, and the otherbranch extending from R025@ by Way of RAZ'IS, RCZ'IB, and the winding ofM238 to battery. Each time the circuit for energizing the rotary magnetM233 is completed and interrupted, this magnet operates to drive thewipers 223 and 2S5 of the rotary switches 29E and 292, respectively,included in the minor switch 296* one step away from their normalpositions. switches 29I and 292 are driven away from their normalpositions the switch springs 235 are actuated into engagement, therebyto prepare a circuit traced hereinafter for energizing the transferrelay R', this circuit being interrupted at The relay R230 follows the'When the wipers noted of the rotary' this time, at RA2 52, by theoperated relay R256. In response to this digit the Wipers 293 and 295 ofthe rotary switchesv 29| and`292,'respectively, are driven a niunber ofsteps away from their normal positions corresponding to this dialeddigit and into engagement with corresponding contacts in the associatedcontact banks 294 and 296, respectively. At the conclusion of the fourthdigit the line relay R235 reoperates, thereby to interrupt, atRA23i andRC233, the circuit for energizing in multiple the relay Rz'ii and therotary magnet M238 in order to cause the relay R253 to restore `shortlythereafter and to arrest further operation of the rotary magnet M233.Upon restoring, the relay Ri'iii completes, at RA252, the.previously'rnentioned circuit for energizing the transfer relay Ril,this circuit extending from ground, at the switch springs 235, by Way ofthe switch springs 235, RA252, and the winding of REEG to battery. Whenthus energized the relay R266 operates to complete, at RA2F5I, anobvious holding circuit vfor energizing the winding thereof, tointerrupt, at RAZZand RCZli, a further point in the previously tracedcircuit for energizing in multiple the relay R253 and the rotary magnetM238, and to prepare, at RAZSE and RC2S3, a circuit traced hereinafterfor energizing the relay RZIt.

Shortly after the conclusion of the fourth digit dialed the subscriberat the substation A replaces the receiver of the telephone instrumentthereat upon its hook, thereby to interrupt the loop circuit extendingtothe line relay RZSQ in order to cause the latter relay tol restore. Uponrestoring, the relay R2i! completes, at RA23I and RC233, the previouslymentioned circuit for energizing the relay RZIil, this circuit extendingfrom ground, at RA23I, by way of RC233, RAME, RAZER, RC263, RAEEB, andthe winding of R2Iil to battery. When thus energized the relay R230operates to complete, at RAZI I, an obvious path for applying groundpotential to the ringing machine start lead C205, to prepare, at RA2i2,a holding circuit traced hereinafter for energizing the switch-throughrelay RER, "to complete, at RAZIS, a path extending from battery, at.the winding of R220, by way of the winding of R22t, RA22A5, RC225, andRARIB to the ring pick-up lead C2I5 for applying battery potential to C2iii, and to complete, at RAZIIi, an obvious holding circuit forenergizing the hold relay R24li. The hold rela-y R246, being of theslow-to-release type, does not restore incident to the restoration ofthe line relay R238, and is retained in its operated position over theabove-mentioned holding circuit for energizing the winding thereof. Ac-

cordingly, ground potential is not removed from the control conductorCH2 of the trunk line Il!! incident to the restoration of the line relayR230.

Shortly thereafter and at the beginning of a code ringing cycle, groundpotential is applied in the ringing machine to the ring pick-up leadC2I5, thereby .to complete a circuit for energizing the switch-throughrelay R220, this circuit extending from the groundedring pick-up leadCZIE by way of RA2I3, RC226, `RA225, and the Winding of R226 to battery.When thus energized the relay R226 operates to complete, at RAEZO. andRA225, a holding circuit for energizing the Winding thereof extendingfrom ground, at RAZiZ, by way of RAEZA, RA225, and the winding of R229to battery, and to interrupt, at RA225 and RC226, the original circuitfor energizing the winding thereof by Way o-f the ring pick-up leadC2I5. Also'gthe krelay R220 interrupts, at RAZZI `and RC2`22, andat'RA22i and RC223, further points in the loop circuit for energizingthe line relay R23il, and completes, at RA22Il and RC223, and at RA22`Iand RC228, points in a circuit traced hereinafter for projecting ringingcurrent from the ringing machine associated with the trunk line 2% byWay of the operated reverting call switch 200, the trunk line Iii), andthe linkr ISI! over the sub# scriber line 1563,'the exact circuit forprojecting inging current from the ringing machine associated with thetrunk line Z over the subscriber line ISE] depending upon the positionsof the Wipers of the rotary switches included in the minor switches 'Zimkand '390, in a manner more fully described subsequently.

As previously noted, a divided ringing circuit is employed in thesystem, a rst group or" subscriber substations associated with eachparty line `having ringers thereat connected between one line conductorof the party line and ground, and a second group of subscribersubstations associated With each party line having ringers thereatconnectedbetween the other line conductor of the party line and ground.The oper# ation of the reverting call switch Zii depends upon whetherthe calling and called subscriber substations A and B are in the sainegroup. In the event these subscriber substations are in the same group,the reverting call switch 203 operates to cause ringing current of thecode corresponding to the called subscriber substation to be projectedover the line conductor 'of the sube scriber line Iil, to which theringers at each of the subscriber substations A and B are connected. inthe event these subscriber substations are in different groups, thereverting call switch Edil operates first to cause ringing current oflthe code corresponding to the called subscriber substation to beprojected over the line conductor of the subscriber line idto which theringer at the called substation B is connected, and then to causeringing current of the code corresponding to the calling subscribersubstation to be projected over the line conductor of the subscriberrline Iil, to which the ringer at the calling sub-- station A isconnected. Also, itis noted that the subscriber substations associatedwithV the subn scriber line 50 and having ringers connected to one lineconductor thereof are assigneddirectory numbers comprising a third odddigit, and the subscriber substations associated with the subscriberline Ibi) and having ringers connected to the other line conductorthereof are assigned rectory numbers comprising a third even digit.

Assuming that the third digit of the directory number of the callingsubscriber substation A'is l, the No. l, and the third digit of thedirectory number of the called subscriber substationvB is the No. 3, thewipers of the rotary switches oi the minor switch 280 engage the rstcontacts in the associated contact banks, and the wipers of the rotaryswitches of the minor switch 29!) engage the third contacts in theassociated contact banks. At this time a circuit. is completed forprojecting ringing current of the code corresponding to the calledsubscriber substation B over the subscriber line Idil, this circuitextending from the ungrounded terminal of the ringing machine winding byWay of the ringing conductor M3, the third contact in the contact bank2M and the associated wiper 233 of the rotary switch 2ilI, the upperwinding of the ring cut-off relay R255,

YRCZLZt, and RAZZI, to the line conductor Ci'I of the trunk line i119,and rtherefrom -by-way of the operated link |00, the line conductor C|5|of the subscriber line |50, and a condenser and the ringer at the calledsubstation B, to ground. Also, a circuit is prepared for energizing theupper winding of the ring cut-oir relay R255, which is completed whenthe subscriber at the substation B answers the call by removing thereceiver of the telephone instrument thereat from its hook, this circuitextending, when completed, by way of the previously traced path to theline conductor C5| of the subscriber line |55, and therefrom by way ofthe bridge path at the substation B between the line conductors C15! andC|52 of the subscriber line |50, C|52, the operated link |00, the lineconductor CH3 of the trunk line |10, RA22?, RC228, and the windings 202and 203 of the transformer 20| to ground.

Assuming that the third digit or the directory number ofthe callingsubscriber substation A is the No. 2, and the third digit of thedirectory number of the called subscriber substation B is the No. 4, thewipers of the rotary switches of the minor switch 280 engage the secondcontacts in the associated contact banks, and the wipers of the rotaryswitches of the minor switch 200 engage the fourth contacts intheassociated contact banks. At this time a circuit is completed forprojecting ringing current of the Code corresponding to the calledsubscriber substation B over the subscriber line |50, this circuitextending from the ungrounded terminal of the ringing machine winding byway of the ringing conductor M4, the fourth contact in the contact bank295 and the associated wiper 295 oi the rotary switch 292, and thewindings 205 and 200 of the transformer 20i to ground at RA220. Thisringing current traversing the windings 204 and 205 of the transformer20| induces a correspondingy ringing current in the windings 202 and 203thereof, which traverses a path extending from ground by way of thewindings 203 and 202, RC22B, RA221, to the line conductor CH3 of thetrunk line |10, and therefrom by way of the operated link |00, the lineconductor C|52 of the subscriber line |50, and the condenser and theringer at the called substation B to ground. Also, a circuit is preparedfor energizing the upper winding of the cut-oil relay R255, which iscompleted when the subscriber at the substation B answers the call byremoving the receiver of the telephone instrument thereat from its hook,this circuit extending, when` completed, from battery at the resistor20?, by way of the resistor 201, the second contact in the contact bank280 and the associated wiper 203 of the rotary switch 28|, the fourthcontact in the contact bank 204 and the associated wiper 293 of therotary switch 20|, the upper winding of R255, HC22-3, RAZZI, the lineconductor Ci 'H of the trunk line |10, and the operated link |00 to theline conductor C|5|, and therefrom by way of the bridge path at thesubstation B between the line conductors C|5| and C|52 of the subscriberline |50, and a portion of the previously traced circuit to ground, atthe winding 203 of the transformer 20|.

Assuming that the third digit of the directory number of the callingsubscriber substation A is the No. l, and the third digit of thedirectory number of the called subscriber substation B is the No. 2, thewipers of the rotary switches of the minor switch 200 engage the firstcontacts in the associated contact banks, and the wipers of the rotaryswitches of the minor switch 200 engage the second contacts in theassociated contact banks. At this time a circuit is completed forprojecting ringing current of the code corresponding to the calledsubscriber substation B over the subscriber line |50, this circuitextending from the ungrounded terminal of the ringing machine winding byway of the ringing con- 'I ductor M2, the second contact in the contactbank 296 and the associated wiper '295 of the rotary switch 292, and thewindings 205 and 204 of the transformer 20| to ground at RA220. Thisringing current traversing the windings 204 and 205 of the transformer20| induces a corresponding ringing current in the windings 202 and 203thereof which is projected by way of the previously traced path over theline conductor C|52 of the subscriber line |50 to ground at the ringerat the called substation B. Also a circuit is completed for projectingringing current of the code corresponding to the calling subscribersubstation A over the subscriber line |50, this circuit extending fromthe ungrounded terminal of the ringing machine winding by way of theringing conductor Ml, the first contact in the contact bank 285 and theassociated `wiper 2830i the rotary switch 28|, the second contact in thecontact bank 204 and the associated wiper 293 of the rotary switch 29|,the upper winding of the ring cut-01T relay R255, RC223, RAZZI, the lineconductor Cl'H of the trunk line |10, the operated link |00, the lineconductor C|5| of the subscriber line |50, and a condenser and theringer at the calling substation A to ground. The ringing machineoperates to complete the circuits for applying ringing currents to theringing conductors MI to M5, inclusive, sequentially, thereby to causethe ringer at the called substation B and the ringer at the callingsubstation A to be operated alternatively. Also a circuit is preparedfor energizing the upper winding of the ring cut-off relay R255, whichis completed when the subscriber at the substation B answers the call byremoving the receiver of the telephone instrument thereat from its hook,this circuit extending, when completed, from the ringing conductor Ml byway of the previously traced path to ground at the winding 203 of thetransformer,

Assuming that the third digit of th`e directory number of the callingsubscriber substation A is the No. 2, and the third digit of thedirectory number of the Acalled subscriber substation B is f,

the No. l, the wipers of the rotary switches of the minor. switch 280engage the second contacts in the associated contact banks, and thewipers of the rotary switches of the minor switch 290 engage the firstcontacts in the associated con-;

tact banks. At this time a circuit is completed for projecting ringingcurrent of the code corresponding to the called subscriber substation Bover the subscriber line I 50, this circuit extending from theungrounded terminal of the ringing machine winding by way of the ringingconductor MI, the iirst contact in the contact bank 294 and theassociated wiper 293 of the rotary switch 20|, the upper winding of R255and a portion of the previously traced circuit including the lineconductor C|5| of the subscriber line |50 to ground at the ringer at thecalled substation B. Also a circuit is completed for projecting ringingcurrent of the code corresponding to the calling substation A over thesubscriber line |50, this circuit extending from the ungrounded terminal0f the ringing machine winding by way of the ringing conductor M2, thesecond contact in the contact bank 286 and the associated wiper 285 ofthe rotary switch 282, the

rst contact in the contact bank 296'and the associated wiper 295 of therotary switch 292, and the windings 205 and 200 of the transformer 20`I`to ground, at RA220. This ringing current traversing the windings 204and 205 of the transformer 20! induces a corresponding ringing currentin the windings 202 and 203 thereof which is projected by way of thepreviously traced circuit including the line conductor C|52 of thesubscriber line |50 to ground at the ringer at the calling substation A.As previously noted, the ringers at the called and calling subscribersubstations B and A, respectively, are Operated alternatively. Also acircuit is prepared for energizing the upper winding of the ring cut-offrelay R255, which is completed when the subscriber at the substation Banswers the call by removing the receiver of the telephone instrumentthereat from its hook, this circuit extending, when completed, from theringing conductor MI by way of the previously traced path to ground atthe winding 203 of the transformer 20|.

When the subscriber at the called substation B answers the call, one ofthe previously traced circuits for energizing the up-per winding of thering cut-01T relay R255 is completed, depending upon whether the callingand called substations A and B, respectively, are in the same ordifferent groups, as previously noted. When thus energized the ringcut-off relay R255 operates to complete, at RA251, a holding circuit forenergizing the lower winding thereof, this circuit extending fromground, at RAZM, by way of RA251 and the lower winding of R255 tobattery. Also the relay R255 interrupts, at RA256, the previously tracedpath for applying ground potential to the control conductor CH2 of thetrunk line |10, and interrupts, at RA258, the circuit for energizing therelay R2 I0, thereby to cause the latter relay to restore. Uponrestoring, the relay R2 |9 interrupts, at RA2| l, the previously tracedpath for applying ground potential to the ringing machine start leadC206 in order to arrest further operation of the ringing machineassociated with the reverting call switch 200, to interrupt, at RA2|2,the holding circuit for energizing the relay R220 in order to cause thelatter relay to restore, and to interrupt, at RA2I4, the previouslytraced holding circuit for energizing the hold relay R200. Shortlythereafter the hold relay R220 restores to interrupt, at RA244, theholding circuit for energizing the lower winding of the ring cutoffrelay R255 in order to cause the latter relay to restore shortlythereafter, and to complete, at vRANG, a circuit for energizing therelease magnet M239 of the minor switch 250, this circuit extending fromground. at RA245, by way of RA2S5, RCZSE, and the winding of M239 tobattery. When this energized the release magnet M239 operates to-release the wipers of the rotary switches 29| and 292 of the minorswitch 290, thereby to cause these wipers to be returned to their normalpositions. When the wipers noted of the rotary switches of the minorswitch 280 are returned to their normal positions, the switch springs235 are actuated into disengagement, thereby to interrupt the holdingcircuit for energizing the transfer relay R250. The transfer relay R260then restores to interrupt, at RA265 and H6266, the circuit forenergizing the release magnet M239, and to complete, at RA255 and R026?,a circuit for energizing the release magnet M231 of the minor switch230, this circuit extending from ground, at RA246, by way of RA265,RCZB'I,

RAZ'H, and the `winding of R231v to battery. When thus energized therelease magnet M231 operates to release the wipers of the rotaryswitches 20| and 282 of the minor switch 280, thereby to cause thesewipers to be returned to their normal positions. When the Wipers notedof the rotary switches of the minor switch 280 are returned to theirnormal positions, the switch springs 230 are actuated intodisengagement, thereby to interrupt the holding circuit for energizingthe transfer relay R270. The transfer relay R270 then restores tointerrupt, at RAZll, the circuit for energizing the release magnet M231.Upon restoring, the hold relay R200, the

ring cut-off relay R255, and the transfer relay..

at the called substation B to interrupt, at RA256,

the path for applying ground potential to the control conductor CI'I2 ofthe trunk line I'lil, thereby to interrupt the previously traced holdingcircuit for energizing the lower winding-of the cut-off magnet RI|0 inthe line circuit |20 individually associated with the subscriber line|50. The cut-olf magnet RI Ill then restores, to complete, at RAIH andRCN? and at RAMI and RCI a bridge circuit for energizing the windings of the linemagnet R520, thereby to retain this line magnet in itsoperated position. This circuit extends from ground at the lower windingof RI 20 by way of the lower winding of RI20, RAIll', RCII'I, CI52, thebridge path including the telephone instrument at the called subscribersubstation B between the line conductors C|52 and CI5| of the subscriberline |50, C|5I, RCIH, RA||| and the upper winding of R|20 to battery.lAlso,lupon restoring, the cuto magnet Rl I0 interrupts, at RAI IIi andRAI Il', the previously traced holding circuit for energizing the lowerwinding of the line magnet R|20, interrupts, at RAI I4 and RCI I0, afurther point in the holding circuit for energizing the lower windingthereof, interrupts, at RAI I2 and RCI 2, a further point in thepreviously traced path for applying ground potential by way of thecontrol conductor CI53 of the subscriber line |50 to the controlconductor CI54 thereof, and completes, v

at RAI i3 and RCI I3, the previously traced path for applying groundpotential, at RC! I3, to the control conductor CI54 of the subscriberline |50 extending to the contact banks of the Strowger mechanismsincluded in the connector switches of the` links having access thereto,thereby to mark the subscriber line |59 as busy. Finally, the cut-offmagnet R|I0 completes, at RA|5 and ROMS, the previously mentioned pathfor applying ground potential to the control `conductor C|5 extending tothe permanent alarm, this path extending from ground at RC|I5 by way ofRAl I5, RCI25, RA|25, RA|25 and RCIZS to the control conductor OISE.This application of ground potential to the control conductor C |56causes the permanent alarm device associated therewith to be actuated,thereby to indicate to an operator that the subscriber line |50 is busyon a reverting call or due to a permanent `fault thereof thereon. Due tothe fact that the bridge circuit for energizing the upper and lowerwindings of the line magnet RIZil is completed at RCIII and RAIII and atRAII'I and RCEIT prior to the interruption of the holding circuit forenergizing the lower winding thereof at RAI I6 and RAI Il, as previouslynoted, the line magnet RIZ!) remains in its operated position. At thistime the line circuit m4 is operated to lock the subscriber line I5!!out of service; and talking battery is supplied by way of the previouslytraced bridge circuit to the telephone instrument at the calledsubscriber substation B.

As previously noted, when the subscriber at the called substation Banswers the call the reverting call switch 200 is-released, thereby tointerrupt the circuit for projecting ringing current over the subscriberline I5!) in order to cause further operation of the ringer at thecalling subscriber substation A to be arrested. When the operation ofthe ringer at the calling subscriber substation A is arrested, thesubscriber thereat is advised that the subscriber at the calledsubstation B has answered the call. The subscriber at the substation Athen removes the receiver of the telephone instrument thereat from itshook, thereby to complete an established connection between the callingand called subscriber substations A and B, respectively, for two-waycommunication therebetween, talking battery being supplied to thesubstation A by way of the previously traced bridge circuit.

The release of this established connection between the subscribersubstations A and B is under the control of the last subscriber toreplace the receiver of the telephone instrument at his substation uponits hook. When the last subscriber replaces the receiver of thetelephone instrument at his substation upon its hook, the bridge circuitfor energizing the upper and lower windings of the line magnet RIZIB isinterrupted, thereby to cause this line magnet to restore, as previouslynoted. At this time the established connection between the subscribersubstations A and B is completely released, and the line circuit |04individually associated with the subscriber line I5@ is released,thereby to mark this subscriber line asv idle to the finder andconnector switches of the links having access thereto.

It will be understood that a reverting call which is to be extended fromthe subscriber substation C to the subscriber substation lD is firstinitiated at the substation C by removing the receiver of the telephoneinstrument thereat from its hook and is subsequently completed to thesubstation D in the manner that the previously described reverting callfrom the substation A was extended to the substation B. The release ofthis established connection is under the control of the last party toreplace the receiver of the telephone instrument at his substation uponits hook, as previously noted.

Also it is noted that a timing arrangement is incorporated in theconnector switch H32 which is operative in the event the switch-throughrelay therein does not operate within a predetermined time interval, dueto the fact that the connector switch has not been fully operated toseize a line accessible thereto, to cause ground potential to be removedfrom the wiper ISI. For example, the link im) may be seized in thepreviously described manner by the appearance of a fault on one of thesubscriber lines, in which case the connector switch H32 thereof wouldnot be operated subsequently to seize a line accessible thereto in orderto cause the operation of the switch-through relay therein, wherebyground potential would be removed from the wiper IBI, as previouslynoted. Under these conditions where ground potential is removed from thewiper IBI, the holding circuit for energizing the cut-off magnet in theline circuit associated with the line having the fault thereon isinterrupted, thereby to cause the cut-off magnet to restore. Uponrestoring, the cut-off magnet in the line circuit associated with theline having the fault thereon Causes the line to be locked out ofservice in the manner described previously in connection with theextension of a reverting call between the subscriber substations A andB. Also, ground potential is' applied to the control conductorassociated therewith extending to the permanent alarm device, thereby tocause the permanent alarm device to be operated. The operation of thepermanent alarm device for an unreasonable time interval indicates to anoperator that the associated-4 line is locked out of service upon apermanent fault thereon rather than merely being busy due to a revertingcall thereon.

While there has been described what is at present considered to be thepreferred embodiment o the invention, it will be understood that variousmodifications may be made therein, and it is intended to cover in theappended claims all such modifications as fall within the true spiritand scope of the invention.

What is claimed is:

l. A line circuit adapted for use in a telephone system including a lineaccessible to an automatic switch, said line circuit comprising, incombination, line and cut-oil relays, a first contact set operativelyassociated with said line relay, a second Contact set operativelyassociated with said cut-off relay, a third Contact set, means normallyeirective operatively to associate said third contact set with said linerelay, each of said contact sets having a normal position and beingoperative away trom its normal position in response to the operation ofthe one of said relays with which it is operatively associated, meansresponsive to the creation o a calling condition on said line for 'Icausing said line relay to be operated, means responsive to the seizureof said line by said automatic switch for causing said cut-oif relay tobe operated, means controlled by the operation of said cut-oit relay forrendering said rstmen tioned means ineective, additional meanscontrolled by the operation of said second contact set away from itsnormal position for causing said line relay to be operated, and circuitsfor controlling said automatic switch governed in aocordance with thepositions of said contact sets.

2. A line circuit adapted for use in a telephone system including a lineaccessible to an automatic switch, said line circuit comprising, incombination, line and cut-oi relays, a first contact set operativelyassociated with said line relay, a second contact set operativelyassociated with said cut-01T relay, a third contact set, mechanicalmeans for operatively associating said third contact set with said linerelay, each of said contact sets having a normal position and beingoperative away from its normal position in response to the operation ofthe one of said relays with which it is operatively associated,

said line relay being operative in response to the creation of a callingcondition on said line, said cut-oif` relay being operative in responseto the seizure oi said line by said automatic switch, means controlledby the operation of said cutoi relay for actuating said mechanicalmeans,

fai

tig.)

tir

till) additional means controlled by the operation of said secondcontact set away from its normal position for causing said line relay tobe operated, and circuits for controlling said automatic switch governedin accordance with the positions of said contact sets. y

3. A line circuit adapted for use in a telephone system including a lineprovided with at least one-line conductor `and accessible to anautomatic switch, said line circuit comprising, in combination, line andcut-oilc relays, a rst contact set operatively associated with said linerelay, a second contact set operatively associated with said cut-offrelay, a vthird contact set, means normally elective operatively toassociate said third contact set with said line relay, each of saidcontact vsets having a normal position and being operative away from itsnormal position in response to the operation of the one of said relayswith which it is operatively associated, a first circuit including saidline conductor for said line relay, a holding circuit for said linerelay, said rst lcircuit being completed in response to the creation ofa calling condition on said line, whereby said line relay is operated,said cut-off relay being operative in response to the seizure of saidline by said automatic switch, means controlled by the operation of saidcut-off relay for rendering said first-mentioned means ineiective,whereby said third contact set is returned to its normal position, meanscontrolled by the operation of said second contact set away from itsnormal position for completing said holding circuit and for interruptingsaid rst circuit, whereby said line relay is retained operated, andcircuits for controlling said automatic switch governed in accordancewith the positions of said contact sets.

4. A line circuit adapted foruse in a telephone system including a lineprovided with at least one line conductor andA accessible to anautomatic switch, said line circuit comprising, in combination, line andcut-olie relays, a rst contact set operatively associated with said'linerelay, a

second contact set operatively associated with said cut-oli relay, athird contact set, mechanical means for operatively associating saidthird contact set with said line relay, each of said contact sets havinga normal position and being operative away from its normal position inre sponse to theoperation of the one of said relays with which it isoperatively associated, a rst circuit including said line conductor forsaid line relay, a holding circuit for said line relay, said irstcircuit being completed in response to the creation of a callingcondition on said line, whereby said line relay is operated, saidcut-off relay being operative in response to the seizure of said line bysaid automatic switch, means controlled by the operation f said cut-offrelay for actuating said mechanical means, whereby said third contactset is returned to its normal position, means controlled by theoperation of said second contact set away from its normal position forcompleting said holding circuit and for inter'- rupting said rstcircuit, whereby said line relay is retained operated, and circuits forcontrolling said automatic switch governed in accordance with thepositions of said contact sets.

5. In a telephone system, a line, a number of automatic switches havingaccess to said line, a line circuit associated with said line andincluding line and cut-oli relays, a first contact set operativelyassociated with said line relay, a second contact set operativelyassociated with said cut-off relay, a third *contact set', meansnormally effective operatively to associate said third contact set withsaid line relay, each of said contact sets having a normal position andbeing operative away fromiits normal position in response to theoperation of the one of said relays with which it is operativelyassociated, means responsive to the creation of a calling condition onsaid line for causing said line relay to be operated, control meansoperative in response to the operation of said rst and third contactsets away from -their `normal positions for causing an idle one of saidautomatic switches to seize said line, means responsive to the seizureof said line by said one automatic switch for causing said cut-oli relayto be` operated, means controlled by the operation of said cut-on relayfor rendering said first-mentioned means ineffective, whereby said thirdcontact set is returned to its normal position, means controlled by thereturn of said third contact set to its normal position for arrestingthe operation of said control means, and additional circuits forcontrolling said automatic switches governed in accordance with thepositions of said Contact sets.

6.'In a telephone system, a line, a number .of inder switches havingaccess to said line, a line circuit associated with said line andincluding line and cut-01T relays, a distributor associated with saidnder switches and operative to cause an idle one of said finder switchesto operate and seize a line marked as a calling line, a rst contact setoperatively associated with said line relay, a second contact setoperatively associated with said cut-offrelay, a third contact set,means normally effective operatively to associate said third contact'set with said line relay, each of said contact sets having a normalposition and being operative away from its normal position in responseto the operation of the one'of said relays with which it is operativelyassociated, means responsive to the creation of a calling condition onsaid line for causing said line relayto be operated, means controlled bythe .operation of said iirst and third contact sets away from theirnormal positions for initiating operation of said distributor and formarking said line as a calling line, means responsive to the seizure ofsaid line by one of said finder switches for causing saidcut-off relayto be operated, means controlled bythe operation of said cut-oi relayfor rendering said first-mentioned means inelective, whereby said thirdcontact set is returned to its normal position, and means controlled bythe return of said `third contact set to its normal 'position forarresting the operation of said distributor. y

'7. In a telephone system, a line, a number. of nder switches havingaccess to said line, aline circuit associated with said line andincluding line and cut-oi relays, a distributor associated with saidiinder switches and operative to cause an idle one of said nder switchesto operate and seize a line marked as a calling line, a iirst contactset operatively associated with said `line relay, a second contact setoperatively associated with said cut-off relay, a third Contact set,mechanical means forv operatively associating said third contact setwith said line relay,'e`ach of said contact sets having a normalposition and being operative away from its normal position in responseto the operation of the one of said relays with which it is operativelyassociated, means responsive to the creation of a calling condition onsaid line for causing said line relay `to be operated, means controlledby the operation of said rst and third contact sets away from theirnormal positions for initiating operation of said distributor and formarking said line as a calling line, means responsive to the seizure ofsaid line by one of said finder switches for causing said cut-ofi relayto be operated, means controlled by the operation of said cut-off relayfor actuating saidv mechanical means, whereby said third contact set isreturned to its normal position, and means controlled by the return ofsaid third contact set to its normal position for arresting theoperation of said distributor.

8. In a telephone system, a line provided with at least one lineconductor, a number of nder switches having access to said line, a linecircuit associated with said line and including line and cut-oil"relays, a distributor associated with said finder switches and operativeto cause an idle one of said finder switches to operate and seize a linemarked as a calling line, a first contact set operatively associatedwith said line relay, a second contact set operatively associated withsaid cutoii relay, a third contact set, mechanical means lor operativelyassociating said third contact set with said line relay, each of saidContact sets having a normal position and being operative away from itsnormal position in response to the operation of the one of said relayswith which it is operatively associated, a rst circuit including saidline conductor for said line relay, a holding circuit for said linerelay, means responsive to the creation of a calling condition on saidline for causing said first circuit to be completed, whereby said linerelay is operated, means controlled by the operation of said irst andthird Contact sets away from their normal positions for initiatingoperation of said distributor and for marking said line as a callingline, means responsive to the seizure of said line by one of said nderswitches for causing said cut-off relay to be operated, means controlledby the operation of said cut-oi relay for actuating said mechanicalmeans, whereby said third contact set is returned to its normalposition, means controlled by the operation of said second contact setaway from its normal position for completing said holding circuit andfor interrupting said first circuit, whereby said line relay is retainedoperated, and means controlled by the return of said third Contact setto its normal position for arresting the operation of said distributor.

9. A line circuit adapted for use in a telephone system including a lineaccessible to a number of automatic switches, said line circuitcomprising, in combination, line and cut-01T relays, a first contact setoperatively associated with said line relay, a second contact setoperatively associated with said cut-off relay, a third contact set,means normally effective operatively to associate said third contact setwith said line relay, each of said contact sets having a normal positionand being operative away from its normal position in responseto theoperation of the one of said relays with which it is operativelyassociated, means responsive to the creation of a calling condition 'onsaid line for causing said line relay to be operated, means responsiveto the seizure of said line by one of said automatic switches forcausing said cut-ofi relay to be operated, means controlled by theoperation of said cut-oi relay for rendering said first-mentioned meansineiective, whereby said third contact set is returned to its normalposition, means controlled by the operation of said second contact setaway from its normal position for causing said line relay to beretained-operated, means for releasing said one automatic switch, meansresponsive to the release 01 said one automatic switch for causing saidcut-off relay to be restored, means controlled by the return of saidsecond contact set to its normal position for causing said line relay toremain operated in the event a calling condition remains on said line,and means controlled when said first contact set is operated away fromits normal position and said second and third contact sets are returnedto their normal positions for marking said line as busy to saidautomatic switches.

l0. A line circuit adapted for use in a telephone system including aline accessible to a number of automatic switches, said line circuitcomprising, in combination, line and cut-oit relays, a rst contact setoperatively associated with said line relay, a second contact setoperatively associated with said cut-off relay, a third contact set,mechanical means for operatively associating said third 'contact setwith said line relay, each of said contact sets having a normal positionand being operative away from its normal position in response to theoperation of the one of said relays with which it is operativelyassociated, said line relay being operative in response to the creationof a calling condition on said line, said cut-off relay being operativein response to the seizure of said line by one of said automaticswitches, means controlled by the loperation of said cut-off relay foractuating said mechanical means, whereby said third contact set isreturned to its normal position, means controlled'by the operation ofsaid second contact set away from its normal position for causing saidline relay to be retained operated, means for releasing said oneautomatic switch, said cut-off relay being restored in response to therelease of said one automatic switch, said line relay remaining operatedsubsequent to the return of said second contact set to its normalposition in the event a calling condition remains on said line, andmeans controlled when said first contact set is operated away from itsnormal position and said second and third contact sets are returned totheir normal positions for marking said line as busy to said automaticswitches.

il. A line circuit adapted for use in a telephone system including aline provided with at least one line conductor and accessible to anumber of automatic switches, said line circuit comprising, incombination, line and cut-off relays, a first contact set operativelyassociated with said line relay, a second contact set operativelyassociated with said cut-oit relay, a third contact set, means normallyeffective operatively to associate said third contact set with said linerelay,`

each of said contact sets having a normal position and being operativeaway from its normal position in response to the operation of the one ofsaid relays with which it is operatively associated, a iirst circuitincluding said line conductor for said line relay, a holding circuit forsaid line relay, said first circuit being completed in response to thecreation of a calling condition on said line, whereby said line relay isoperated, said cutoff relaybeing operative in response to the seizure ofsaid line by one of said automatic switches, means controlled by theoperation of said cutoff relay for rendering said first-mentioned meansineffective, whereby said third Contact set is returned to its normalposition, means controlled by the operation of said second contact setaway from its normal position for completing said holding circuit andYfor' interrupting said rst' circuit, whereby said line 'relay lisLretained operated, means f for f releasing `said# one automatic switch,said cut-oi relay being lrestored i in response zto theA release of saidone automatic switch,-fmeans controlled -by the returnfof saidfsecond-4contact set to its `normal Aposition for completing` said ilrst circuitand 'for interrupting said'holdng circuit, whereby'said line relayremains loperated to said'secondv positiony in-'theevent afcalling-condition -remains onV said line, and means-controlled when saidrst contactset-is operated 'awayfrom its-normal position and-saidsecondandethird contact sets are returnedto'ftheirhnormal 'positions formarking -saidlineas busy to f said lautomatic switches.

' 12. In a telephone systemfaline-a number of automatic -switchesrhaving access lto-'said"\line, a i line circuit -associated with` said*line andl including line land cut-'01T relays, a 'first contact setoperatively associated with-said@line relay, a-"second contact set'operativelyfassocia-ted-fwith said cut-oif relay,` al third contact'set, meansfnormally effective voperatively to associatersaidfthirdcontactset with said'line relayeach ofesaid-` contact setshaving anormal position and-'beingI operative away from its normal `position in-response to theV operation-ofthe one vof said-V relays with which it isoperatively associated;- means/responsive to the creation of-'acall-ing-condition-"on said line for causing saidline relayto beoperated; means controlled bythe operationof said "rst and third contactsets -awayfromtheir normal-positions for causing an -idleione of saidautomatic switches to seize said-line,=meansre sponsive to-the seizureof said line bysaid-one automatic switch for causing saidvcuteoff relay'to be operated, means controllediby-the oper- -ation of said cut-offkrelay ifor rendering sa-id rst-mentionedmeans ineiective, whereby saidthirdcontactI set is-returned to its'fnormal'position, meanscontrolled-'by theA operation of-said second contact set -away ffrom-its normaliposition'for causingsaid line relay to =be retainedoperated, means for releasing -.-said one'Lautomatic switch,-meansresponsive to `the release of `said-one automatic switch for causingsaidcutvoff` relay to be restored', meansY controlled by the returnof-saidv-second contact set to its normal position'for causing said`line relay to remain -operated inthe eventra calling"condition-'remainsonsaid line, -andI-means controlled "when said iirst contact set isoperated awayffromf its 'normallrposition and saidesecond andv-thirdfcontact sets` are returned to their fnormalpo'sitionsrformarking said line as Abusy to said -automati switches.

13. In a' telephone system, a line,v a numberof nder andconnectorrswitches'havingaccess to said line, a-line circuitassociatedwith= said *line and including line4 and cut-ofi relays,` a distributorassociated with fsaidnder switchesfand operative to cause an idle one ofsaid fnderswltches to operate and seize Va line-marked as `a callingline, a rst contact setY operatively associated with said line relay, asecondv contact set operatively associated withfsaid cut-off relay, -a-third contact set, means normally effective -op'erativelyto associatesaid' third contactset-with said l-linerelay, each of said contact setshaving-afnormal-position and being operative away from rits normalposition in response to the operation of'they one of `said'relays withwhich@ itis operatively Aasf sociated,2means responsiveto the:creationlof a calling conditiony onsaid line? forI causingdsaid linerelaylto be.V operated; means Vcontrolled by the operation i of :saldifirstv and third contact `setsV away .from'their 'normal upositionsiforinitiatingoperation of said distributor andfforrmarking-isaid'- lineasa'calling .line,'means responsive'to the'seizure 31 .of fsaid line: byone of said nder switches for causingzsaidcut-oii relay to be operated,vmeans ,controlledfby the operation of said cut-off relay -for rendering.said iirst-mentioned 1 means ineiective, vwhereby saidfthirdcontactr'set is returned ato its normal position, means controlled ,bylthe.operation of .said second Contact yset away fromiitsr'normal positionforr causing said line relayztotbe retainedvoperated, means controlled:byltheireturn'fofsaid` third contact set'to its normalzposltioniorarresting the operation of said vdistributor,"means for releasing said.one f-finder .switch,means responsiveto the release of said'one'nderswitch ior'causing said cut-oir relay -torberrestoredmeanscontrolled by the'return` of said y.second :contact settoits normalposition for causing .saidiline relaytoremainoperated -ingthefevent akcalling condition remains on said .line,. andvmeans .controlled whensaid first contact set isuoperatedraway from its normal position andsaidrsecond` contact set is: returnedY to its. normal lposition formarking saidlineas busyto-sad connector switches.

:14.:In yatelephone system, a line, a number -of :iinfderf a-ndconnector `switches having .access to Vlsaid line, a :line circuit;.associated with said line :and-1 including line and cut-.01T 1 relays,a distributorrassociated withfsaid finder .switches .and operative .to/causeran idle one :offsaid finder switches to operate; and seizealinefmarkedas .Aafrcalling'rlinefa Y rst contact setoperativelyassociated with *saidzline-relay,` axsecond contact set i:operatively .associated with said i cut-off 1 relay; a .third contactset; :means normally effective operatively t0 associate said thirdcontact setA with vsaidr-linemelay,l each of said 'contacta sets having.anormal position-and'beingsoperative away from its normal positioninresponse toithe operation .off the oneofsaid"relays.wwith whichitisoperatively associated, meansresponsive-to the creation `of acalling, condition on said line for causing said line:relay'to beoperated; means controlledE .by the- .operation of t said riirstI'aandnthird .contact 'setsaway from theirzfnormal lpositions for.initiating operation of said distributor :and for 'marking said lineasa calling line,ameans: responsive to thefseizure of` said vlinefrbyyone vof said nder` switches r for causing said icut-oii'relayly tobezoperatemmeans controlled bytheoperationof said `cut-off e relay forvrendering. said Arstz-mentioned means ineffectivepwhereby said thirdcon- *tact-set isreturned to its normal position,.;means controlledbythe operation of.y said .secondi` contact set. :away from' itsnormalnposition' for causing said. line relay to `beretaine'd operated;means controlled' by the 'return of4 said! third Contact 'fset to itsnormal position' for. arrestingthe operation of i-said distributor,lmeans `for'releasing lsaid' one nd'er switch-means responsive -to'I-thefrelease of said oneA finder lswitch for causing-.said` cut-'offrelay vto be restored, means controlledI bytheI return offsaid secondcontacts'et vto its'normal position-y for' causingl said line relay; toremain operated in the event a calling .condition remains on said line;:means controlled when-said first contact set isoperated lawayfrom-itsnormal position and 'said' second contact'setds returnedto itsnormal position 'ior1marki-ng1said line as`r busy to said' connectorswitches,- eandlv signalingE means controlled tv-lierresaid-vrstfcontact seti -is operated

